Methods of forming abrasive articles

ABSTRACT

An abrasive article, comprising a polycrystalline material comprising abrasive grains and a filler material having an average negative coefficient of thermal expansion (CTE) within a range of temperatures between about 70 K to about 1500 K. A method of forming an abrasive article, comprising preparing an abrasive material, preparing a filler material having an average negative coefficient of thermal expansion (CTE) within a range of temperatures between about 150 K to about 1500 K, and forming a polycrystalline material comprising grains of the abrasive material and the filler material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/918,314, filed Jun. 14, 2013, which is a continuation of U.S. patentapplication Ser. No. 12/844,666, filed Jul. 27, 2010, now U.S. Pat. No.8,500,833, issued Aug. 6, 2013, which application claims priority toU.S. Provisional Patent Application No. 61/228,897, filed Jul. 27, 2009,titled “Abrasive Article and Method of Forming,” the entire disclosuresof each of which are hereby incorporated herein by reference in theirentireties.

BACKGROUND

1. Field of the Disclosure

The following is directed to abrasive articles, and, more particularly,to abrasive articles of a polycrystalline material comprising anabrasive material and a filler material.

2. Description of the Related Art

Abrasive articles are used in various industries for many differentapplications including, for example, forming, shaping, abrading,cutting, drilling, and finishing. Abrasive articles can also be formedof various shapes and sizes depending upon the intended end use of theabrasive article. Such articles rely upon the delivery of hard materialsto a surface being worked to achieve the end result. Delivery of thehard materials can change depending upon the industry, but aftersufficient use, abrasive articles can become less effective as they tendto wear during use.

Certain abrasives and abrasive materials and the methods of forming suchmaterials have gained interest, because such materials are particularlyhard and capable of withstanding a greater degree of degradation.Accordingly, the industry continues to demand improvements in abrasivearticles.

SUMMARY

According to a first aspect, an abrasive article includes a materialincluding an abrasive material and a filler material having an averagenegative coefficient of thermal expansion (CTE) within a range oftemperatures between about 70 K to about 1500 K.

In another aspect, an abrasive article includes an abrasive materialhaving polycrystalline diamond and a catalyst material, wherein theabrasive material comprises an average coefficient of thermal expansion(CTE) of not greater than about 2.2×10⁻⁶/K within a range oftemperatures between about 70 K to about 1500 K.

In still another aspect, an abrasive article includes a polycrystallinematerial having abrasive grains separated by grain boundaries, whereinthe grain boundaries include a filler material having an averagenegative coefficient of thermal expansion (CTE) within a range oftemperatures between about 70 K to about 1500 K.

According to yet another aspect, an abrasive article includes apolycrystalline material having abrasive grains, a catalyst material,and a material selected from the group of materials consisting oftungstate, molybdate, vanadate, and a combination thereof.

Another aspect is directed to an abrasive article including apolycrystalline material comprising abrasive grains separated by grainboundaries, wherein the grain boundaries comprise a filler materialselected from the group of oxides consisting of AMO₃, AM₂O₈, AM₂O₇,A₂M₃O₁₂, and a combination thereof, wherein A represents a metalelement, M represents a metal element, and O represents oxygen.

In one aspect of the present application, an abrasive article includes asubstrate having an upper surface, an abrasive layer overlying the uppersurface of the substrate, wherein the abrasive layer includes abrasivegrains and an abrasive filler material having an average coefficient ofthermal expansion (CTE) of not greater than zero within a range oftemperatures between about 70 K to about 1500 K.

According to another aspect a method of forming an abrasive articleincludes preparing an abrasive material, preparing a filler material,and forming a polycrystalline material having grains of the abrasivematerial and a filler material having an average negative coefficient ofthermal expansion (CTE) within a range of temperatures between about 70K to about 1500 K.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be better understood, and its numerousfeatures and advantages made apparent to those skilled in the art byreferencing the accompanying drawings.

FIG. 1 includes a flowchart of a process for forming an abrasive articlein accordance with an embodiment.

FIGS. 2A and 2B include illustrations of composite precursor fillermaterial particles in accordance with an embodiment.

FIG. 3 includes an illustration of the microstructure of an abrasivearticle in accordance with an embodiment.

FIG. 4 includes an illustration of the microstructure of an abrasivearticle in accordance with an embodiment.

FIG. 5 includes a perspective view illustration of a cutting elementincorporating an abrasive article in accordance with an embodiment.

The use of the same reference symbols in different drawings indicatessimilar or identical items.

DETAILED DESCRIPTION

The following is generally directed to polycrystalline materials for usein abrasive articles and methods of forming such materials. Thepolycrystalline materials herein can incorporate abrasive materials thatmay be suitable for applications directed to material removal including,for example, grinding, cutting, polishing, and the like. In accordancewith certain embodiments, the articles herein may be particularly suitedfor use in drill bits, such as those used in penetrating rock formationswithin the earth for geothermal, gas, and oil businesses. One example ofsuch a drill bit can include polycrystalline diamond cutter (PDC) drillbits. Still, other applications may be contemplated for thepolycrystalline materials herein, including thermal management devices(e.g., heat sinks), insulators, coatings, and the like. In particularreference to thermal management devices, the material may include amaterial having a particularly suitable thermal transfer coefficient,which can include certain inorganic polycrystalline materials (e.g.,diamond) bonded to some amount of a ceramic (e.g., oxide, carbide,nitride, boride, etc.) bonded to the polycrystalline material.

Referring to FIG. 1, a flowchart is provided illustrating a method offorming an abrasive article in accordance with an embodiment. Asillustrated, the process is initiated at step 101 by preparing anabrasive material. Preparation of an abrasive material can includeselection of an abrasive material. Selection can include choosing anabrasive material based on grade, quality, grain size, and/ordistribution of grain sizes.

In particular, the abrasive material may utilize grain sizes that aresubmicron, nano-size, or a mixture thereof. For example, certainsuitable grains sizes can be not greater than about 200 microns, such asnot greater than about 150 microns, not greater than about 100 microns,not greater than about 75 microns, not greater than about 50 microns, oreven not greater than about 25 microns. Nano-size particles may beparticularly small, generally having an average grain size of notgreater than about 500 nm, such as not greater than about 250 nm, notgreater than about 100 nm, not greater than about 50 nm, or even notgreater than about 1 nm.

Reference herein to abrasive materials can include those materialshaving a Vickers hardness of at least 25 GPa. In other embodiments,these abrasive materials can have a Vickers hardness of at least 30 GPa,such as at least 40 GPa, at least 50 GPa, or even at least about 75 GPa.Still, abrasive materials herein can have a Vickers hardness within arange between about 25 GPa and about 100 GPa, such as between about 30GPa and about 100 GPa, or even between about 40 GPa and about 90 GPa.

The abrasive materials of embodiments here are generally inorganicmaterials. Some examples of abrasive materials include natural orsynthetic materials, such as ceramics, cermets, and the like. Certainabrasive materials can include abrasive materials, superabrasivematerials, or a combination thereof. Some suitable examples of suchmaterials can include diamond, diamond-like-carbon, nitrides, carbides,borides, silicates, and a combination thereof. Carbides may includecarbon combined with a metal element, such that useful carbides includematerials such as titanium carbide, titanium boron carbide, tantalumcarbide, niobium carbide, and a combination thereof. Suitable nitridesmay include certain metal elements bonded to nitrogen including, forexample, aluminum nitride. Silicates can include oxygen and siliconelements bonded together, such as silica, or more particularly may beformed with an additional metal element.

According to one particular embodiment, the abrasive article is formedsuch that the abrasive material consists essentially of diamond, such aspolycrystalline diamond. In other abrasive articles, the abrasivematerial can consist essentially of cubic boron nitride.

After preparing the abrasive material at step 101, the process cancontinue at step 103 by preparing a filler material. Preparation of afiller material can include the same steps as preparing an abrasivematerial, that is, selecting the proper grade, quality, grain size,and/or particle size distribution of filler material. In accordance withcertain embodiments, the filler material can be made of small particleshaving average particle sizes that are submicron (agglomerates orsingle, grain particles), nano-size, or a mixture thereof.

Certain embodiments may utilize a filler material having an averageparticle size that is less than the average particle size of theabrasive material. For example, the average particle size of the fillermaterial can be not greater than about 100 microns, such as not greaterthan about 1 micron, not greater than about 0.5 microns, not greaterthan about 0.1 microns, or even not greater than about 0.05 microns.

Preparation of the filler material can include various processes or acombination of processes depending upon the process selected for formingthe final-formed article. In certain processes, the filler material ofthe final-foamed abrasive article is incorporated initially in theforming process as part of the preparation of the filler material.

Other forming processes may optionally utilize a precursor fillermaterial. A precursor filler material may have a different form than thefiller material present in the final-formed abrasive article. Examplesof different forms include differences in chemical composition, physicalcharacteristic, or combinations thereof. That is, in certain processes,the filler product may differ chemically such that the precursor fillermaterial has a different chemical composition than the intendedfinal-formed filler material. For example, the precursor filler materialcan include a reactant species that is one component of the fillermaterial. Other processes may utilize a precursor filler material havinga physically different form than that of the filler material of thefinal-formed abrasive article. For example, the precursor fillermaterial may be a particle of a different size, shape, design, orcombinations thereof as compared to the filler material of thefinal-formed abrasive article. It will be appreciated that reference tothe filler material of the final-formed abrasive article is reference toa material having particular mechanical characteristics, chemicalcomposition, lattice structure, and a combination thereof.

According to one embodiment, the precursor filler material can include apowder material. The powder material can be formed of a single materialor a combination of materials. In more particular instances, theprecursor filler material can include composite particles. Compositeparticles can include the precursor filler material combined with othermaterials, which may be suitable for forming the final-formed abrasivearticle. Certain materials that may be included in the compositeparticles can include passivation agents, binder materials, alloys, orpure metals that have a non-catalytic activity, a partial or limitedcatalytic activity, or a fully catalytic activity during a formingprocess. Materials having a fully catalytic or partially catalyticactivity can include metals, such as Group VII through Group XI metalelements including, for example, cobalt, iron, and/or nickel.

Certain embodiments can incorporate a composite particle including acore material and a coating layer overlying the core material. One typeof such particle is illustrated in FIG. 2A including a core material 280and a coating layer 281 overlying the core material 280. In utilizingsuch composite particles, the core material 280 can include the fillermaterial of the final-formed abrasive article, a precursor fillermaterial, or a combination thereof. According to one particularembodiment, the core material 280 consists essentially of the fillermaterial. In still other embodiments, the core material 280 consistsessentially of a precursor filler material.

In accordance with those embodiments utilizing a precursor fillermaterial having a core/coating layer design, the coating layer 281 caninclude an inorganic material, an organic material, or a combinationthereof. Suitable inorganic materials can include metals, metal alloys,ceramics, cermets, essentially pure elemental compositions (e.g.,diamond) and a combination thereof. In certain instances, the coatinglayer 281 can be made of a metal or metal alloy material, particularlymetal and/or metal alloy materials containing refractory metalmaterials.

Some suitable organic materials can include natural and/or syntheticmaterials, such as polymers, resins, epoxies, and a combination thereof.It will be appreciated, that depending upon the forming process chosen,certain organic materials may not be present in the final-formedabrasive article, such that the organic material may serve a purpose inthe material and be evolved as a gas or otherwise removed during theforming process.

The coating layer 281 can be formed of a crystalline material, apolycrystalline material, an amorphous material, or a combinationthereof.

In certain designs, the coating layer 281 can include a passivationagent that is a non-catalytic material that does not react with othermaterials of the abrasive article during the forming process. That is, apassivation agent may not necessarily undergo a chemical change orphysical change during the forming process and thereby can mitigate theinteraction of the core material 280 with other chemicals during theforming process such that the core material 280 may retain its chemicalcomposition and/or mechanical properties. The passivation agent can havethose characteristics described above with regard to the coating layer281 (e.g., a polycrystalline material).

The coating layer 281 can be formed such that a majority of the content,by volume, comprises a passivation agent. In other instances, a greateramount of the coating layer 281 comprises the passivation agent, such asat least about 75 vol %, at least about 90 vol %, or even at least about95 vol %. One particular embodiment utilizes a coating layer 281consisting essentially of the passivation agent.

Suitable passivation agents can include certain materials describedherein. For example, the passivation agent can be an inorganic material,such as a metal, metal alloy, ceramic, cermet, essentially pureelemental composition, and a combination thereof. Some suitablepassivation agents can include metal elements from Group III, Group IV,Group V, and Group VI of the Periodic Table of elements. For example,some particular types of metals and metal alloys can include manganese,vanadium, titanium, scandium, zirconia, palladium, molybdenum, tantalum,tungsten, hafnium, platinum, lanthanum, neodymium, niobium, and acombination thereof. Particular examples of metal alloys can includetungsten-based alloys, molybdenum-based alloys, iron-based alloys, and acombination thereof.

In further reference to other passivation agents, some processes canutilize materials such as oxides, carbides, nitrides, borides, diamond,diamond-like carbon, cubic boron nitride, and a combination thereof. Inparticular instances the coating layer can be formed such that itconsists essentially of diamond.

Various processes may be used to form a precursor filler material, andparticularly precursor filler materials having a core/coating layerdesign. For example, the coating layer can be formed on the corematerial through processes such as deposition, spraying, precipitation,plating, mixing, adsorption, absorption, and a combination thereof. Inone particular embodiment, such particles can be made throughliquid-based processes including, for example, a sol-gel process, achemical co-precipitation process, and the like. Such processes caninclude the formation of a mixture utilizing a liquid vehicle andparticles suspended within the liquid vehicle. The particles suspendedwithin the liquid vehicle can include the core material, the coatingmaterial, precursors or chemical reactants of the core material and/orthe coating material. In some embodiments, the precursor filler materialmay include a colloidal suspension including the filler material. Thecolloidal suspension may include a passivation agent. Moreover, in anyof the foregoing processes, utilization of a precursor filler materialcan include utilization of a material having a stoichiometric, oralternatively, a non-stoichiometric composition.

Formation of a precursor filler material may also include a heatingprocess that may be used in combination with or separate from otherprocesses, such as liquid-based processing routine. Heating processesmay be particularly suitable for forming precursor filler materialshaving a core/coating layer design. A heating process can includeapplication of elevated temperatures, generally well above roomtemperature, such as on the order of at least about 200° C., at leastabout 300° C., or even at least about 400° C., to which affect canincorporate a heating process that may facilitate the formation ofsuitable precursor filler material. Notably, heating processes mayutilize particular temperatures, durations, and atmospheres tofacilitate the formation of precursor filler materials.

Drying processes may also be used to facilitate the formation ofprecursor filler materials. In one exemplary process, spray drying canbe utilized to form particles of precursor filler material having acontrollable shape, such as a spherical shape, hollow sphere, oragglomerate.

FIG. 2B includes an illustration of a composite particle according to analternative embodiment. As illustrated, the composite particle can be anagglomerated material, including a plurality of smaller particles 286comprising the core material, and a coating layer 285 overlying each ofthe smaller particles 286. It will be appreciated that while the smallerparticles 286 are illustrated as relatively dispersed throughout thecoating layer 285, in other embodiments, the composite particle caninclude agglomerates of the smaller particles 286.

After preparing a filler material at step 103, the process can continueat step 105 by forming a polycrystalline material comprising grains ofthe abrasive material and a filler material. The forming step caninclude a pre-forming step, which may be undertaken to give thematerials sufficient shape and strength for handling, otherwise referredto as a “green article.” The pre-forming step to produce a green productcan include processes such as pressing, casting, molding, and the likeor a combination thereof. In one particular process, the preformingprocess can include an isostatic forming process to produce a greenarticle prior to other forming processes. Uniaxial die pressing orisostatic pressing can be carried out at a pressure of at least about 50MPa, such as at least about 100 MPa, at least about 250 MPa, or even atleast about 500 MPa.

In accordance with one embodiment, after carrying out any pre-formingprocesses, the process of forming the polycrystalline material canfurther include heating the abrasive material to a forming temperature.The forming temperatures can vary depending upon the nature of theabrasive material, and in certain instances, for example, can be atleast about 1000° C. In other processes, the forming temperature can beat least about 1200° C., such as at least about 1400° C., at least about1600° C., or even at least about 1800° C. Particular embodiments mayutilize a forming temperature between about 1000° C. and about 2200° C.,such as between about 1200° C. and about 2000° C., or even between about1400° C. and about 1800° C.

Forming of the polycrystalline material can also include the applicationof increased pressure (i.e., a forming pressure) from standardatmospheric conditions alone or in combination with other processparameters, such as the application of a forming temperature. Notably,in those instances utilizing a combination of high temperature and highpressure, the process may be considered a high temperature, highpressure (HTHP) process. The forming pressure can be at least about 1GPa to preform the materials, which may be contained in a vessel tofacilitate the application of the elevated pressures. Certain otherforming pressures may be applied to the preform material to affectforming of the abrasive article having the polycrystalline material,such pressures can be at least about 2 GPa, at least about 3 GPa, oreven at least about 4 GPa. According to one embodiment, the formingpressure is within a range between about 1 GPa and about 15 GPa, betweenabout 2 GPa and about 10 GPa between about 3 GPa and about 8 GPa. Itwill be appreciated that utilization of certain nano-size particleswithin the article may alter the forming process, such that in someinstances, higher pressures and shorter durations may be used. Aftermaintaining the forming temperature and/or forming pressure for asufficient time, the article may be cooled. During the cooling process,the article may undergo an annealing process. The annealing can becompleted at a temperature less than the forming temperature. Forexample, the annealing temperature can be at least about 400° C., suchas at least about 500° C., such as at least about 600° C., andparticularly within a range between about 400° C. and about 700° C.

The annealing process may be carried out for an annealing duration of atleast about 30 minutes. In other embodiments, the annealing duration canbe longer, such as on the order of at least about 60 minutes, at leastabout 4 hours, at least about 8 hours, or even at least about 10 hours.Still, certain processes can utilize an annealing duration of less thanabout 24 hours.

The annealing process may be carried out to facilitate the formation ofa filler material having suitable mechanical characteristics, chemicalcomposition, and/or lattice structure. That is, for example, the fillermaterial may have a certain crystalline structure and coefficient ofthermal expansion such that the annealing process facilitatesrearrangement of the filler material after the forming process, whichfacilitates reforming of the crystalline structure of the fillermaterial having suitable mechanical characteristics.

It will be appreciated that other materials may be added to thepolycrystalline material besides the abrasive material and the fillermaterial. For example, a catalyst material may be added to thepolycrystalline material and further may be present in the final-formedpolycrystalline material of the abrasive article. Suitable catalystmaterials can include a metal or metal alloy material. In particular,the catalyst material may include a transition metal element. Inaccordance with one embodiment, the catalyst material can include ametal such as cobalt, iron, nickel, molybdenum, and a combinationthereof.

FIG. 3 includes an illustration of the microstructure of an abrasivearticle in accordance with an embodiment. In particular, FIG. 3 includesan illustration of a polycrystalline material 200 having grains 201comprising an abrasive material as described in embodiments herein. Thepolycrystalline material 200 can also include grain boundaries 202extending between and separating the grains 201. As illustrated, inaccordance with one embodiment, the abrasive article can be formed suchthat the polycrystalline material 200 can contain certain materialswithin the grain boundaries 202, such as a filler material 203, whichcan be present as a single-crystalline phase, a polycrystalline phase,an amorphous phase, or combinations thereof material. Additionally, thegrain boundaries 202 can contain a catalyst material 205 that caninclude those materials described herein. Likewise, the catalystmaterial 205 can be present as a single-crystalline phase, apolycrystalline phase, an amorphous phase, or combinations thereofmaterial.

The abrasive articles according to embodiments herein can be formed suchthat the grains 201 have an average grain size of not greater than about100 microns. In other embodiments, the grains 201 have an average grainsize of not greater than about 75 microns, such as not greater thanabout 50 microns, or even not greater than about 40 microns. Inparticular instances, the grains 201 are formed such that the averagegrain size is within a range between about 0.1 microns and about 40microns, and more particularly between about 0.1 microns and about 25microns. It will be appreciated that the size distribution of the grainscan be controlled. For example, certain abrasive articles can be formedto have a single distribution of grains sizes about a mean grain size(i.e., a generally Gaussian-shaped distribution), a bimodal grain sizedistribution, or any other grain size distribution suitable for theintended application of the article.

In accordance with embodiments herein, the filler material of thefinal-formed abrasive article can be an inorganic material havingsuitable mechanical characteristics, such as a negative thermalexpansion coefficient as described in more detail herein. Suitableinorganic materials can include metals, ceramics, cermets, and acombination thereof. In particular instances, the filler material caninclude an oxide. The oxide material can include a metal element such asa transition metal element, such as zirconium (Zr), hafnium (Hf),tungsten (W), molybdenum (Mo), tin (Sn), uranium (U), thorium (Th),phosphorous (P), vanadium (V), scandium (Sc), aluminum (Al), magnesium(Mg), lanthanum (La), chromium (Cr), iron (Fe), and a combinationthereof. Notably, such oxides can be stoichiometric metal oxidecompounds or non-stoichiometric metal oxide compounds. Certainembodiments can utilize a filler material comprising anisopolyoxometalate.

The filler material can be a polycrystalline material, such that is hasa polycrystalline phase. In other embodiments, the filler material hasan amorphous phase content. Additionally, with reference to the latticestructure of the filler material, generally the filler material can havea cubic, orthorhombic, or combinations thereof crystalline structure.

In particular instances, the filler material of the final-formedabrasive article includes an oxide material selected from the group ofoxides consisting of AMO₃, AM₂O₈, AM₂O₇, A₂M₃O₁₂, and a combinationthereof. In such compositions, the variable “A” represents a metalelement, the variable “M” represents a metal element that is differentfrom the metal element represented by “A”, and the variable “O”represents oxygen. According to embodiments herein, the variable “A”generally represents a metal element from the group of zirconium (Zr),hafnium (Hf), tin (Sn), uranium (U), thorium (Th), scandium (Sc),aluminum (Al), iron (Fe), chromium (Cr), lanthanum (La), and acombination thereof. In certain instances, the metal element representedby the variable “M” can include a metal element such as of tungsten (W),molybdenum (Mo), phosphorous (P), vanadium (V), and a combinationthereof.

In more particular embodiments, the filler material can include atungstate, molybdate, vanadate, and a combination thereof. For example,the polycrystalline material comprises a filler material that is made ofzirconium tungstate. Certain polycrystalline materials may be formedsuch that the filler materials consist essentially, or even entirely of,zirconium tungstate. Some specific exemplary filler materials caninclude Sc₂(WO₄)₃, Zr₂(WO₄)(PO₄)₂, ZrV₂O₇, ZrW₂O₈, Sc₂W₃O₁₂,ZrW_(2-x)Mo_(x)O₈, ZrMo₂O₈, HfW₂O₈, ZrV_(2-x)P_(x)O₇,Zr_(1-x)Hf_(x)W₂O₈, ZrW_(2-x)Mo_(x)O₈, and Zr_(1-x)M_(x)W₂O_(8-y),wherein M represents Sc, In, and Y. Other exemplary filler materials caninclude MgHf(WO₄)₃, MgZr(WO₄)₃, Al₂W₃O₁₂.

According to an alternative embodiments, certain filler materialsfacilitating negative CTE characteristics within the final formedmaterial can include metals such as iron alloys, manganese alloys,chromium alloys, and a combination thereof. In particular instances,such metal materials may be magnetic materials. For example, suitablemetal filler materials can include Lu₂Fe₁₇, Y₂Fe₁₇,Y₂Al₃Fe_(14-x)Mn_(x), Tb₂Fe₁₆Cr, MnF₃, Tb₂Fe_(16.5)Cr_(0.5),Dy₂AlFe₁₀Mn₆, Dy₂AlFe₁₃Mn₃, Y₂Fe₁₆Al; magnets M[N(NC)₂]₂ (M=Co,Ni),Cr—Mn alloys (e.g., base-centered cubic crystalline structures) Zn(CN)₂.

Generally, the polycrystalline material 200 can be formed such that itcontains not greater than about 50 vol % of a filler material. In otherinstances, the amount of filler material in the final-formed abrasivearticle can be less, such as not greater than about 40 vol %, notgreater than about 30 vol %, not greater than about 20 vol %, notgreater than about 15 vol %, not greater than about 10 vol %, or evennot greater than about 5 vol %. In particular instances, thepolycrystalline material can contain between about 1 vol % and 50 vol %,such as between 1 vol % and 40 vol %, between 1 vol % and about 30 vol%, between about 1 vol % and about 20 vol %, or even between 1 vol % and10 vol % of the filler material.

Embodiments herein may utilize a filler material within the final-formedabrasive article that have an average coefficient of thermal expansionthat is not greater than zero within a range of temperatures betweenabout 70 K to about 1500 K. That is, the average coefficient of thermalexpansion over a temperature range, such as between any two temperatureswithin the range of temperatures between 70 K and 1500 K, is negative.Preferably, the average coefficient of thermal expansion is a negativevalue over the entire span of the range from 70 K to 1500 K, but thismay not necessarily be the case for certain materials. In particularinstances, the filler material can have an average coefficient ofthermal expansion that is less than zero, that is, a negative averagecoefficient of thermal expansion within a range of temperatures betweenabout 70 K to about 1500 K. For example, some filler materials can havean average negative coefficient of thermal expansion of not greater thanabout −0.1×10⁻⁶/K, such as not greater than about −1.0×10⁻⁶/K, notgreater than about −2.0×10⁻⁶/K, or even not greater than about−5.0×10⁻⁶/K over the range of temperatures between about 70 K to about1500 K. Particular abrasive articles can incorporate a filler materialhaving an average negative coefficient of thermal expansion within arange between about −0.1×10⁻⁶/K and about −20×10⁻⁶/K, such as betweenabout −1.0×10⁻⁶/K and about −18×10⁻⁶/K, and even between about−2.0×10⁻⁶/K and about −15×10⁻⁶/K over the range of temperatures betweenabout 70 K to about 1500 K.

In particular instances, the filler material comprises a material havingan isotropic negative coefficient of thermal expansion. The isotropicnature of the thermal expansion characteristic facilitates equal anduniform volume decrease, as opposed to an anisotropic volumetric change.

As described in accordance with embodiments herein, the polycrystallinematerial of the final-formed abrasive article can be formed such that itincludes a passivation agent. Such a passivation agent may be presentwithin the particles of the filler material, and may be bonded directlyto the filler material. In some materials, the passivation agent may bepresent within the grain boundary 202. In still other instances, thepassivation agent may be present with the catalyst material 205, and mayeven more particularly, be bonded directly to the catalyst material 205.In still other instances, the passivation agent may be present withinthe crystalline grains 201 of the polycrystalline material 200. Thepassivation agent can include those materials described previouslyherein. It will also be appreciated that the passivation agent can bedispersed throughout the polycrystalline material 200 in various phases,including the grains 201, the grain boundaries 202, or a combinationthereof.

The passivation agent can have a particular average coefficient ofthermal expansion (CTE) of not greater than about 20×10⁻⁶/K over therange of temperatures between about 70 K to about 1500 K. Otherembodiments may utilize a passivation agent having an average CTE of notgreater than about 15×10⁻⁶/K, such as not greater than about 10×10⁻⁶/K,not greater than about 8×10⁻⁶/K over the range of temperatures betweenabout 70 K to about 1500 K. Certain embodiments may utilize an averageCTE for the passivation agent within a range between about 0.1×10⁻⁶/Kand about 20×10⁻⁶/K, such as between about 1×10⁻⁶/K and about 15×10⁻⁶/Kover the range of temperatures between about 70 K to about 1500 K.

Generally, the polycrystalline material is formed such that it comprisesa minor amount of the passivation agent. For example, suitable amountsof the passivation agent can include not greater than about 10 vol %. Inother embodiments, this content may be less, such as not greater thanabout 8 vol %, such as not greater than about 5 vol %, and particularlywithin a range between about 1 vol % and 10 vol %, and even moreparticularly between about 1 vol % and about 5 vol %.

As described herein, the polycrystalline material 200 can include acertain content of catalyst material 205. The catalyst material 205 maybe present in an amount of not greater than about 20 vol %. In otherinstances, the polycrystalline material can include an amount ofcatalyst material that is not greater than about 15 vol %, such as notgreater than about 12 vol %, not greater than about 10 vol %, or evennot greater than about 8 vol %. Particular embodiments can utilize anamount of catalyst material within a range between about 1 vol % and 20vol %, such as between about 1 vol % and about 15 vol %. It will beappreciated that various methods exist to provide the catalyst materialwithin the polycrystalline material. For example, the catalyst materialmay be present within the initial preformed material of thepolycrystalline material. Alternatively, the catalyst material may bepresent within a material layer adjacent the polycrystalline materialduring forming, and the catalyst material moves from the adjacentmaterial layer into the polycrystalline layer during formation.

The catalyst material 205 can include those materials previouslydescribed herein. Moreover, the catalyst material 205 as illustrated inFIG. 2, may be present within the grain boundaries 202. Additionally,the catalyst material may be present at an external surface of thepolycrystalline material, and more particularly at an external surfaceof the abrasive article. That is, for example, the abrasive article maybe formed such that it may not necessarily undergo additional processesto remove a portion of the catalyst material. Still, it may be suitableto undergo a removal process to leach a certain amount of the catalystmaterial from the polycrystalline material.

The catalyst material can have a particular average coefficient ofthermal expansion (CTE) of not greater than about 15×10⁻⁶/K over therange of temperatures between about 70 K to about 1500 K. Otherembodiments may utilize a catalyst material having an average CTE of notgreater than about 10×10⁻⁶/K, such as not greater than about 8×10⁻⁶/K,not greater than about 5×10⁻⁶/K over the range of temperatures betweenabout 70 K to about 1500 K. Certain embodiments may utilize an averageCTE for the catalyst material within a range between about 0.1×10⁻⁶/Kand about 15×10⁻⁶/K, such as between about 1×10⁻⁶/K and about 10×10⁻⁶/K,or more particularly between about 1×10⁻⁶/K and about 8×10⁻⁶/K, over therange of temperatures between about 70 K to about 1500 K.

FIG. 4 includes an illustration of the microstructure of an abrasivearticle in accordance with an embodiment. Unlike the polycrystallinematerial 200 of FIG. 3, the polycrystalline material 250 of FIG. 4illustrates grains 201, 209 and 210, which can include differentmaterials. For example, the grains 201 can include the abrasivematerial, while the grains 209 and 210 can include the filler material.Accordingly, embodiments herein may utilize a polycrystalline material,wherein a portion of the grains comprise an abrasive material, and aportion of the grains comprise one or more filler materials. Notably, insome instances, a portion of the grains 209 and 210 consist essentiallyof the filler material. The filler material 203 can have an averagecrystalline size, represented by the grains 209 and 210 that isapproximately the same size of the grains 201 made of the abrasivematerial, and significantly greater in size as compared to the catalyst205 material contained within the grain boundaries 202.

As additionally shown in FIG. 4, the polycrystalline material 250 can beformed such that the catalyst material 205 is contained within the grainboundaries 202. The grains 201 comprising the abrasive material, grains209 and 210 comprising the filler material, and catalyst material 205 ofthe polycrystalline material 250 can be the same as those described inaccordance with other embodiments. It will be appreciated that dependingupon the intended application, polycrystalline materials having themicrostructure of FIG. 4, can have various amounts of grains comprisingthe abrasive material as compared to the amount of grains having thefiller material. Moreover, the grains 209 and 210 can contain the sametype of filler material or a different type of filler material. That is,certain embodiments may utilize a polycrystalline material having afirst type of filler grain (e.g., grain 209) and a second type of fillergrain (e.g., grain 210).

FIG. 5 includes a perspective view image of a cutting element 400 foruse in a drill bit in accordance with an embodiment. The cutting element400 can include a substrate 401 having an upper surface and an abrasivelayer 403 overlying the upper surface. As illustrated, the abrasivelayer 403 can include a chamfer surface 405 angled with respect to aside surface 406 and upper surface 407 of the abrasive layer 403. Theabrasive layer 403 can include a polycrystalline material as describedin accordance with embodiments herein. Notably, the cutting element 400can be formed such that the abrasive layer 403 includes a fillermaterial as described in accordance with embodiments herein.

Additionally, the substrate 401 can be formed such that it includes asubstrate filler material. The substrate filler material can be amaterial having an average coefficient of thermal expansion of notgreater than zero within a range of temperatures between 70 K and about1500 K. In other embodiments, the substrate 401 includes a substratefiller material having a negative average coefficient of thermalexpansion within a range of temperatures between 70 K and about 1500 K.

The substrate 401 can have a substrate filler material that is differentthan the abrasive filler material of the abrasive layer 403. Suchmaterials can be compositionally different from each other, that is,different in their chemical compositions. In other embodiments, thesubstrate filler material and the abrasive filler material can havedifferent average coefficients of thermal expansion within a range oftemperatures of 70 K and about 1500 K.

In some instances, the cutting element 400 can be formed such that thesubstrate 401 has a greater content, as measured in weight percent, ofthe substrate filler material than the content of abrasive fillermaterial present within the abrasive layer 403. Provision of such acutting element 400 may facilitate reduction in mechanical strain,particularly through thermal generated stresses due to a CTE mismatchbetween the abrasive layer 403 and substrate 401.

Articles according to embodiments herein can include abrasive materialsthat can have particularly low average coefficients of thermalexpansion. For example, materials herein can have an average coefficientof thermal expansion (CTE) of not greater than about 15×10⁻⁶/K within arange of temperatures between about 70 K to about 1500 K. In fact, someof the polycrystalline abrasive materials can have a lower CTE, such asnot greater than about 12×10⁻⁶/K, not greater than about 10×10⁻⁶/K, notgreater than about 8.0×10⁻⁶/K, not greater than about 6.0×10⁻⁶/K, notgreater than about 5.0×10⁻⁶/K, and even not greater than about4.0×10⁻⁶/K. Particular embodiments may utilize an abrasive materialhaving an average coefficient of thermal expansion within a rangebetween about 0.1×10⁻⁶/K and about 15×10⁻⁶/K, such as between about0.1×10⁻⁶/K and about 12×10⁻⁶/K, between about 0.1×10⁻⁶/K and about10×10⁻⁶/K, between about 0.1×10⁻⁶/K and about 8.0×10⁻⁶/K, between about0.1×10⁻⁶/K and about 6.0×10⁻⁶/K, between about 0.1×10⁻⁶/K and about5.0×10⁻⁶/K, and even between about 0.1×10⁻⁶/K and about 4.0×10⁻⁶/K.

Certain articles herein can incorporate superabrasive materials, such asdiamond (e.g., polycrystalline diamond) and/or cubic boron nitride. Inparticular reference to the articles incorporating such materials, theaverage coefficient of thermal expansion can be particularly low. Forexample, the article incorporating an abrasive can have an averagecoefficient of thermal expansion (CTE) of not greater than about4.5×10⁻⁶/K within a range of temperatures between about 70 K to about1500 K. In fact, some of the polycrystalline abrasive materials can havea lower CTE, such as not greater than about 4.2×10⁻⁶/K, not greater thanabout 4.0×10⁻⁶/K, not greater than about 3.8×10⁻⁶/K, not greater thanabout 3.5×10⁻⁶/K, not greater than about 3.3×10⁻⁶/K, not greater thanabout 3.0×10⁻⁶/K, not greater than about 2.8×10⁻⁶/K, not greater thanabout 2.5×10⁻⁶/K, not greater than about 2.2×10⁻⁶/K, not greater thanabout 2.0×10⁻⁶/K, not greater than about 1.9×10⁻⁶/K, not greater thanabout 1.8×10⁻⁶/K, or even not greater than about 1.6×10⁻⁶/K within arange of temperatures between about 70 K to about 1500 K. Particularembodiments may utilize an abrasive material having an averagecoefficient of thermal expansion within a range between about 1.0×10⁻⁶/Kand about 4.2×10⁻⁶/K, such as between about 1.1×10⁶/K and about4.0×10⁻⁶/K, between about 1.0×10⁻⁶/K and about 4.0×10⁶/K, between about1.0×10⁶/K and about 3.5×10⁶/K, between about 1.0×10⁻⁶/K and about3.0×10⁻⁶/K, between about 1.0×10⁶/K and about 2.8×10⁶/K, between about1.0×10⁻⁶/K and about 2.5×10⁻⁶/K, and more particularly between about1.2×10⁻⁶/K and about 2.0×10⁻⁶/K within a range of temperatures betweenabout 70 K to about 1500 K.

The abrasive layer 403 can be formed such that it has an averagethickness of at least about 0.5 mm. For example, the abrasive layer 403can be formed such that it has an average thickness of at least about0.75 mm, such as at least about 1 mm, at least about 1.3 mm, at leastabout 2 mm, or even at least about 3 mm. In particular instances, theabrasive layer 403 is formed such that it has a thickness within a rangebetween 0.5 mm and about 5 mm, between about 0.75 mm and about 4 mm, andmore particularly between about 0.75 mm and about 3 mm.

In certain embodiments, the interface between the substrate 401 and theabrasive layer 403 can be modified in light of modifications to theresidual stresses between the abrasive layer 403 and substrate 401 basedon incorporation of the substrate filler material and abrasive fillermaterial. For example, some embodiments may opt for a substantiallyplanar interface contour between the substrate 401 and the abrasivelayer 403. In other embodiments, the interface can have a non-planarcontour.

The abrasive layer 403 can be formed such that it includes multiplelayers or films of material. The individual layers within the abrasivelayer 403 can be stacked on top of each other, such that a first layeris adjacent to the substrate 401, a second layer is spaced from thesubstrate 401 and overlying the first layer. Any number of layers can beused. The layers can be formed such that each of the layers can be madeof a different abrasive material. Notably, the abrasive material candiffer based on grade, grain size, and/or grain shape. For example, thefirst layer of abrasive material can contain a larger average grain sizethan a second, overlying layer of abrasive material.

Moreover, in embodiments utilizing an abrasive layer 403 having multiplelayers of material, each of the discrete layers can contain a differenttype of filler material. Additionally, each of the layers can contain adifferent amount of filler material. For example, the first layer ofabrasive material, can include a greater content of an abrasive fillermaterial than a second layer of abrasive material overlying the firstlayer. It will be appreciated that various combinations of amounts offiller material combined with the number of layers of abrasive materialcan be utilized.

The above-disclosed subject matter is to be considered illustrative, andnot restrictive, and the appended claims are intended to cover all suchmodifications, enhancements, and other embodiments, which fall withinthe true scope of the present invention. Thus, to the maximum extentallowed by law, the scope of the present invention is to be determinedby the broadest permissible interpretation of the following claims andtheir equivalents, and shall not be restricted or limited by theforegoing detailed description.

In the foregoing Detailed Description, various features may be groupedtogether or described in a single embodiment for the purpose ofstreamlining the disclosure. This disclosure is not to be interpreted asreflecting an intention that the claimed embodiments require morefeatures than are expressly recited in each claim. Rather, as thefollowing claims reflect, inventive subject matter may be directed toless than all features of any of the disclosed embodiments. Thus, thefollowing claims are incorporated into the Detailed Description, witheach claim standing on its own as defining separately claimed subjectmatter.

1. An abrasive article, comprising: a polycrystalline materialcomprising abrasive grains separated by grain boundaries, wherein thegrain boundaries comprise a filler material having an average negativecoefficient of thermal expansion (CTE) within a range of temperaturesbetween about 70 K to about 1500 K, wherein the filler comprises atleast one of a tungstate, a molybdate and a vanadate.
 2. An abrasivearticle, comprising: a substrate having an upper surface; and anabrasive layer overlying the upper surface of the substrate, wherein theabrasive layer comprises abrasive grains and a filler material, whereinthe filler material has an average coefficient of thermal expansion(CTE) of not greater than zero within a range of temperatures betweenabout 70 K and about 1500 K, and wherein the filler material comprisesan isopolyoxometalate.
 3. The abrasive article of claim 2, wherein thefiller material has an average negative coefficient of thermal expansion(CTE) within a range of temperatures between about 70 K to about 1500 K.4. The abrasive article of claim 2, wherein the filler material comprisea material in a polycrystalline phase.
 5. The abrasive article of claim2, wherein the abrasive grains exhibit an average grain size from about0.1 μm to about 40 μm.
 6. The abrasive article of claim 1, furthercomprising a passivation agent dispersed throughout the polycrystallinematerial.
 7. The abrasive article of claim 6, wherein the passivationagent exhibits a CTE of not greater than about 20×10⁻⁶/K within a rangeof temperatures between about 70 K to about 1500 K.
 8. The abrasivearticle of claim 7, wherein the passivation agent exhibits a CTE fromabout 1×10⁻⁶/K to about 15×10⁻⁶/K within a range of temperatures betweenabout 70 K to about 1500 K.
 9. The abrasive article of claim 6, whereinthe passivation agent comprises at least one material selected from thegroup consisting of metals, metal alloys, ceramics, and cermets.
 10. Theabrasive article of claim 9, wherein the passivation agent comprises atleast one material selected from the group consisting of elements fromGroup III, Group IV, Group V, and Group VI of the Periodic Table ofElements.
 11. The abrasive article of claim 10, wherein the passivationagent comprises at least one material selected from the group consistingof Mn, V, Ti, Sc, Zr, Pd, Mo, Ta, W, Hf, Pt, La, Nd, and Nb.
 12. Theabrasive article of claim 6, wherein the polycrystalline materialcomprises from about 1% to about 10% passivation agent by volume. 13.The abrasive article of claim 12, wherein the polycrystalline materialcomprises from about 1% to about 5% passivation agent by volume.
 14. Theabrasive article of claim 2, wherein the filler material comprises amaterial selected from the group of oxides consisting of AMO₃, AM₂O₈,AM₂O₇, A₂M₃O₁₂, and a combination thereof, wherein A represents a metalelement, M represents a metal element different from the metal elementrepresented by A, and O represents oxygen.
 15. The abrasive article ofclaim 14, wherein A represents at least one metal selected from thegroup consisting of Zr, Hf, Sn, U, Th, Sc, Al, Fe, and Cr.
 16. Theabrasive article of claim 14, wherein M represents at least one metalselected from the group consisting of W, Mo, P, and V.
 17. The abrasivearticle of claim 1, wherein the filler material comprises zirconiumtungstate.
 18. The abrasive article of claim 1, wherein thepolycrystalline material comprises from about 1% to about 50% fillermaterial by volume.
 19. The abrasive article of claim 18, wherein thepolycrystalline material comprises from about 1% to about 10% fillermaterial by volume.
 20. The abrasive article of claim 1, wherein thepolycrystalline material further comprises a catalyst materialexhibiting a CTE from about 0.1×10⁻⁶/K to about 15×10⁻⁶/K within a rangeof temperatures between about 70 K to about 1500 K.